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Free keywords:
apatite; phosphate; doping; 3d-metal oxides
Abstract:
Strontium phosphate apatites with compositions Sr-5(PO4)(3)Zn0.15O0.3(OH)(0.7), Sr-5(PO4)(3)Ni0.2O0.4(OH)(0.6), and Sr-5(PO4)(3)Co0.2O0.5(OH)(0.4) were synthesized by solid state reaction at 1400 degrees C in air. The samples were characterized by powder X-ray diffraction, EDX analysis, magnetic measurements and IR spectroscopy. The crystal structures were refined by the Rietveld method in the space group P6(3)/m with lattice constants a = 9.7499(1), 9.7722(1), 9.7507(1) angstrom and c = 7.3066(1), 7.2962(1), 7.2988(1) angstrom, respectively. The 3d-metal atoms were found randomly distributed in the hexagonal channels formally substituting hydrogen in the initial hydroxyapatite. Zn and Ni atoms were twofold coordinated by oxygen atoms such that the linear O-M-O groups formed in the channel separated by the OH groups. Co atom was shifted from the channel center giving the O-Co-O fragment distorted from a linear geometry probably due to the additional coordination by the oxygen atoms of the phosphate groups. (c) 2006 Elsevier Masson SAS. All rights reserved.
